An expedient strategy for the diversity-oriented synthesis of macrocyclic compounds with natural product-like characteristics

Article abstract of DOI:10.1016/j.tet.2015.10.061

Naturally-derived macrocyclic compounds are associated with a diverse range of biological activities, including antibacterial effects, and there are over 100 marketed macrocycle drugs derived from natural products. However, synthetic macrocycles are widely considered to be poorly explored in antibiotic development (indeed, within drug discovery in general). This has been attributed to challenges associated with the generation of such compounds. Whilst there are synthetic methods that can produce large collections of structurally similar macrocycles (i.e., compounds with varying appendages based around similar core macrocyclic ring architectures) there is a relative dearth of strategies for the efficient generation of more structurally diverse macrocycle collections in which there is greater variation in the nature of macrocyclic scaffolds present. Such macrocycle collections should contain compounds with a broad range of biological activities (including antibacterial activities) and the requisite robust synthetic methodology useful for analogue synthesis and lead optimization once an active compound has been identified in a biological screen. Herein, we describe a new and expedient diversity-oriented synthesis (DOS) strategy for the generation of a library of novel structurally diverse macrocyclic compounds with a high level of scaffold diversity. The strategy is concise, proceeds from readily-available starting materials, is modular in nature and features a variety of macrocyclisation techniques. In this proof-of-concept study, the synthesis of several previously unreported macrocyclic compounds was achieved. Each of these macrocycles was based around a distinct molecular scaffold and contained natural product-like structural features (e.g., three-dimensionality and multiple hydrogen bond donors and acceptors) as well as synthetic handles for potential further elaboration. The successful generation of these macrocycles demonstrates the feasibility of the new DOS strategy as a synthetic platform for library generation.

Full text of DOI:10.1016/j.tet.2015.10.061

Tetrahedron xxx (2015) 1e12
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
An expedient strategy for the diversity-oriented synthesis of
macrocyclic compounds with natural product-like characteristics
Joe J. Ciardiello, Warren R.J.D. Galloway, Cornelius J. O’Connor, Hannah F. Sore,
Jamie E. Stokes, Yuteng Wu, David R. Spring *
Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 30 July 2015
Received in revised form 19 October 2015
Accepted 21 October 2015
Available online xxx
Naturally-derived macrocyclic compounds are associated with a diverse range of biological activities,
including antibacterial effects, and there are over 100 marketed macrocycle drugs derived from natural
products. However, synthetic macrocycles are widely considered to be poorly explored in antibiotic
development (indeed, within drug discovery in general). This has been attributed to challenges associ-
ated with the generation of such compounds. Whilst there are synthetic methods that can produce large
collections of structurally similar macrocycles (i.e., compounds with varying appendages based around
similar core macrocyclic ring architectures) there is a relative dearth of strategies for the efficient gen-
eration of more structurally diverse macrocycle collections in which there is greater variation in the
nature of macrocyclic scaffolds present. Such macrocycle collections should contain compounds with
a broad range of biological activities (including antibacterial activities) and the requisite robust synthetic
methodology useful for analogue synthesis and lead optimization once an active compound has been
identified in a biological screen. Herein, we describe a new and expedient diversity-oriented synthesis
Keywords:
Macrocycles
Diversity-oriented synthesis
Scaffold
Chemical space
(
DOS) strategy for the generation of a library of novel structurally diverse macrocyclic compounds with
a high level of scaffold diversity. The strategy is concise, proceeds from readily-available starting ma-
terials, is modular in nature and features a variety of macrocyclisation techniques. In this proof-of-
concept study, the synthesis of several previously unreported macrocyclic compounds was achieved.
Each of these macrocycles was based around a distinct molecular scaffold and contained natural product-
like structural features (e.g., three-dimensionality and multiple hydrogen bond donors and acceptors) as
well as synthetic handles for potential further elaboration. The successful generation of these macro-
cycles demonstrates the feasibility of the new DOS strategy as a synthetic platform for library generation.
Ó 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license
(
http://creativecommons.org/licenses/by/4.0/).
1
. Introduction
Lead compounds for antibacterial chemotherapy can be ob-
tained from two sources: nature (natural products) or de novo
chemical synthesis. Historically, nature has been by far the more
1
The inexorable rise in antibiotic-resistant bacteria has led to
a steady decline in the efficacy of existing therapies for the treat-
important; most of the major classes of antibiotics in therapeutic
use are natural products or semi-synthetic derivatives thereof.
Among these, a macrocyclic scaffold (a ring system of 12 or more
atoms) is common (Fig. 1). Indeed, naturally-derived macrocycles
1,2
1,3
ment of bacterial infections. Moreover, the pace at which new
antibacterial agents are being generated has decreased dramati-
cally in recent decades, a legacy of insufficient investment in fun-
damental antibacterial research by pharmaceutical companies
since the 1960s.1 Consequently, humanity is facing the very real
and disturbing possibility of a future without an effective method
for the treatment of some common bacterial infections.1,2 Thus,
there is a clear and critical medical need for the discovery of novel
antibiotics.1
constitute a large class of compounds with useful antibacterial
,2
4e6
properties.
Natural macrocyclic derivatives are also associated
with a broad range of other attractive biological effects (including
5,7
anticancer, antifungal and immunosuppressive activities)
and
there are more than 100 marketed macrocyle drugs derived from
,3
8
natural products. The diverse and interesting biological activities
associated with the macrocyclic compound class has been attrib-
7,8
uted to characteristic structural features. Their cyclic structure
means that they have less conformational freedom than an equiv-
alent acylic compound and so suffer a smaller entropic loss upon
*
Corresponding author. Fax: þ44(0)1223 336362; e-mail address: spring@ch.
cam.ac.uk (D.R. Spring).
http://dx.doi.org/10.1016/j.tet.2015.10.061
0
040-4020/Ó 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Please cite this article in press as: Ciardiello, J. J.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2015.10.061

2
J.J. Ciardiello et al. / Tetrahedron xxx (2015) 1e12
with higher levels of scaffold diversity would be expected to pro-
vide a higher hit rate against a broader range of targets than li-
braries with lower scaffold, and thus overall structural,
14,15
diversity.
Scaffold diverse macrocycle collections would there-
fore be expected to be particularly valuable in biological screens
where the nature of the biological target is unknown (e.g., in
15,18
phenotypic screening).
In addition, efficient access to structur-
ally diverse macrocycles necessitates the development of synthetic
methodology which is robust and broadly applicable in nature,
which should facilitate the lead optimization process once a hit
11,19
compound has been identified.
Diversity-oriented synthesis (DOS) is a field of organic chemis-
try directed towards the efficient generation of molecular libraries
that incorporate high degrees of structural diversity, including
15,20e22
scaffold diversity.
The screening of DOS libraries has led to
the identification of numerous novel biologically active small
3
,15,23e28
molecules, including several with antibacterial activities.
Recent years have seen the development of several DOS-type
strategies specifically targeted at macrocyclic structures including
9
,10,14,19,27,29e33
examples from our own research group.
However,
there remains considerable scope for further developments in the
field. From a synthesis perspective, there are improvements that
can be made in terms of the expediency of library construction and
19
the efficiency in which scaffold diversity is generated. In addition,
large areas of macrocyclic chemical space, that may contain mole-
cules with exciting biological properties (e.g., critically needed new
antibacterials), still remain under-explored. These considerations
highlight the need for new and expedient DOS strategies towards
previously undescribed macrocyclic compounds. Herein, we de-
scribe work towards the development of one such strategy, which is
based around the use of readily-accessible phenolic carbonyls as
key starting materials. In a proof-of-concept study the synthesis of
several structurally diverse and previously unreported macrocyclic
scaffolds was achieved, which provides a validation of this DOS
strategy as a synthetic platform for library generation.
Fig. 1. Some examples of naturally-derived antibiotics which are based around mac-
rocyclic scaffolds (highlighted in bold). Erythromycin A (1) and Fidaxomicin (3) are
natural products and Azithromycin (2) is a semi-synthetic compound.5
binding to a biological target.7e9 However, unlike smaller cyclic
systems, macrocycles retain a certain flexibility, allowing them to
potentially mould to a target surface in order to maximize binding
interactions.7
e9
In addition, macrocycles can potentially adopt
conformations in which polar motifs are buried away, leading to
improved membrane permeability relative to their linear
analogues.7
Clearly, macrocycles represent attractive targets in the search
for new lead compounds for antibiotic development (indeed, drug
2. Results and discussion
4
,7,8
development in general).
However, naturally occurring macro-
2.1. Outline of the synthetic strategy
cycles are often highly complex in structure, which hampers their
4
,7,10
synthetic modification and pharmacokinetic optimization.
Many DOS pathways are based around a three-phase build/
2
0
Thus, attention has shifted in recent years towards the explora-
tion of synthetic macrocycles of medium complexity in drug dis-
There has been notable success in this field, with many
biologically active synthetic macrocycles with appropriate phar-
couple/pair (B/C/P) algorithm. In the build phase, starting mate-
rials (or building blocks) are synthesized. These are then combined
(coupled together) in the couple phase to yield densely function-
alized substrates for the subsequent pair phase, which involves
7,10
covery.
10
macokinetic profiles identified
(including antibacterial lead
intramolecular reactions that join pairwise combinations of func-
compounds1 ). However, despite these encouraging examples,
1,12
tional groups to generate distinct molecular scaffolds.
14,20
In recent
synthetic macrocycles are still widely considered to be relatively
years, the use of iterative couple steps (i.e., B/C/C/P, B/C/C/C/P, etc.)
7
e10,13
underexplored within drug discovery in general.
This has
has been exploited as a means to increase the diversity of scaffolds
14,34
been attributed to challenges associated with the synthesis of such
compounds, particularly in the context of the formation of the
accessible from a given set of building blocks.
For example, we
have recently reported a DOS strategy towards macrocyclic pepti-
7,9
14
macrocyclic ring architecture. Where present in a small molecule,
the macrocyclic ring is generally considered to serve as the mo-
lecular scaffold (i.e., the core rigidifying structural feature of
a molecule).14 Whilst there are synthetic methods that can produce
large collections of structurally similar macrocycles (i.e., com-
pounds with varying appendages based around similar core mac-
rocyclic scaffolds) there is a relative dearth of strategies for the
efficient generation of more structurally diverse macrocycle col-
lections in which there is greater variation in the nature of mac-
domimetic scaffolds that incorporates iterative couple steps. It
was thought that the iterative couple concept could be used as the
basis for a new and expedient DOS strategy towards novel and di-
verse macrocyclic compounds. We conceived the use of readily-
accessible phenolic compounds of the general form 4, which bear
an electrophilic carbonyl group and a nucleophilic hydroxyl group,
as key starting materials (Scheme 1). It was hoped that each given
aromatic compound would serve as a ‘platform’ onto which dif-
ferent building blocks (generated in the build phase of the DOS)
could be attached through functionalisation of these two reactive
sites (couple stages). This would then afford a range of distinct
acyclic precursors, which could then undergo intramolecular re-
actions to furnish different macrocyclic compounds, each based
around a distinct molecular scaffold (pair phases). More specifically,
we envisaged the use of four general types of building blocks: the
10,14
rocyclic scaffolds present.
This is a crucial issue in the context of
biological screening, since the overall structural, and thus func-
tional diversity of a compound set (i.e., the range of biological ac-
tivities displayed by the compounds) is known to be highly
dependent upon the variety of molecular scaffolds present (the
scaffold diversity) of the collection.1
5e17
Macrocyclic collections
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J.J. Ciardiello et al. / Tetrahedron xxx (2015) 1e12
3
Scheme 1. Outline of the DOS strategy towards structurally diverse macrocyclic compounds of the general forms 14e16. The shaded shapes represent scaffold-defining elements
i.e., regions that can be varied to obtain different macrocyclic scaffolds). LG¼a leaving group (e.g., a halogen).
(
aforementioned aromatic ‘platform’ building blocks 4 (which
would contain an aldehyde or a carboxylic acid moiety together
with the hydroxyl group), together with ‘hydroxyl capping’ build-
ing blocks 5 and 6 ‘carbonyl capping’ building blocks 7 and 8 (cyclic
and acyclic amines in both cases) and malonic acid (9), a ‘spacer’
building block. It was anticipated that the ‘platform’ aromatic
building blocks 4 could be functionalised at the hydroxyl position (a
couple phase) by reaction with the appropriate ‘hydroxyl capping’
building block 5 or 6 to furnish compounds of the general form 10
and 11 (from aromatic carboxylic acids and aromatic aldehydes,
respectively, Scheme 1). Subsequent functionalisation of the car-
bonyl moieties with the appropriate ‘carbonyl capping’ building
block 7 or 8 (a couple phase) would generate compounds of the
general form 12 (by amide bond formation from 10) and 13 (by
reductive amination from 11). Compounds of the form 12 and 13
contain functional groups that could then potentially be reacted
together intramolecularly in the subsequent pair phase of the DOS
to access diverse macrocyclic scaffolds (B/C/C/P pathways).
Specifically, compounds 12 contain a terminal alkyne and terminal
azide group; it was envisaged that a regioselective metal-catalysed
‘click’-type 1,3-dipolar cycloaddition would thus furnish macrocy-
clic architectures of the general form 14 containing either 1,5-
disubstituted triazoles (ruthenium catalysis) or 1,4-disubstituted
triazoles (copper catalysis).
In the case of compounds 13, which contain two terminal alkene
moieties, it was hoped that an intramolecular ring-closing me-
tathesis reaction could be carried out to yield macrocyclic scaffolds
of the general form 15. Furthermore, it was envisaged that larger-
sized macrocyclic structures 16 could be accessed by extension of
the aldehyde moiety of key branchepoint compounds 11 by an
additional couple step with the ‘spacer’ building block 9 (a Knoe-
venagel condensation) to form compounds 17. Subsequent carbonyl
capping with building blocks 8 would generate compounds 18
which contain a terminal alkene and a terminal alkyne. Ring-
closing ene-yne metathesis would then furnish the target com-
pounds 16 (the pair stage). This would formally constitute a B/C/C/
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4
J.J. Ciardiello et al. / Tetrahedron xxx (2015) 1e12
C/P pathway. These larger-sized macrocycles may be better able to
target extended binding interfaces (such as those associated with
example of macrocyles of the general form 20, it was thought that it
would be interesting to examine whether an additional synthetic
handle for post-cyclisation structural elaboration could be installed
which was orthogonal to the alkene unit introduced during
macrocyclisation.
proteineprotein interactions) than the smaller-sized compounds
resulting from a single couple step.1
4,35
Overall, we anticipated that
the DOS strategy outlined in Scheme 1 would allow access to novel
and structurally diverse macrocyclic compounds of three different
structural forms 14e16. Several attractive features of the proposed
DOS strategy were identified. It is step-efficient from readily
available building blocks. Furthermore, it is inherently modular in
nature. Thus, it was anticipated that high levels of structural di-
versity could be achieved in an expedient fashion through the use
of a small set of building-blocks. Variation in the scaffold-defining
elements of the building blocks should allow for efficient genera-
tion of scaffold diversity within each general structural form, as
well as providing scope for the installation of diverse achiral and
chiral appendages and potential biomolecular-interacting elements
around the core macrocyclic ring architectures. The use of different
macrocyclisation techniques in the DOS should also offer an ex-
pansion in the number of distinct molecular scaffolds accessible
from a given set of building blocks (relative to strategies which
employ only one method of ring-closure). Furthermore each
method of macrocyclisation should furnish product scaffolds con-
taining different characteristic structural motifs. In the case of ring-
closure by 1,3-dipolar cycloaddition, the resulting products 14 will
contain a triazole ring system, a structural unit which is considered
to act as a peptide bond mimic (both the trans- and the cis-amide
2.2.1. Building block synthesis. Building blocks 9, 22, 25, 27 and 29
could be obtained from commercial sources. Amino-alkyne build-
ing block 23 was readily accessed from commercially available
pyridine-acid 29 in three steps (Scheme 3). Amine protection
generated the N-Boc derivative 30. Propyl phosphonic acid anhy-
dride (T3P) mediated coupling with alkynyl amine 31 furnished
compound 32 and subsequent removal of the Boc group under
acidic conditions yielded the desired building block 23 (isolated as
the HCl-salt). Building block 28 could also be accessed (again as the
corresponding HCl-salt) from 30 by EDC-mediated coupling with
alkynyl alcohol 33 to form 34 followed by Boc deprotection. The
synthesis of acyclic amino-alkene 26 was similarly straightforward.
EDC-mediated coupling of commercially available carboxylic acid
35 and alkenyl alcohol 36 proceeded smoothly to generate ester 37
and subsequent acid-mediated Boc group removal afforded the
target building block 26 (isolated as the HCl-salt). It was envisaged
that azido-bromo ‘hydroxyl capping’ building block 24 could be
generated in situ from the corresponding tosylate derivative 38
when required (see Section 2.2.2) which in turn was readily ob-
tained from alcohol 39.
bond configurations can be mimicked by the 1,4- and 1,5-triazoles,
respectively).1
4,29,36,37
Thus, such products can be considered to be
2.2.2. Synthesis of target compound 19. The synthesis of compound
19 commenced with the esterification of hydroxy benzoic acid
‘platform’ building block 22 to generate compound 40 (Scheme 4).
Coupling with ‘hydroxyl capping’ building block 24 (which was
formed in situ from 38), proceeded smoothly to afford compound
41. Subsequent saponification of the ester moiety under basic
macrocyclic peptidomimetics, a sub-class of macrocycles which is
of considerable interest in drug discovery and which has attracted
significant attention in recent years.
14,38
Macrocyclisation by ring-
closing and ene-yne metathesis would furnish products contain-
ing synthetically versatile functional motifs (alkene and diene
units, respectively) that could potentially serve as synthetic handles
for further derivitisation around the macrocyclic cores. General
structural type 15 is non-peptidic, a sub-class of macrocyles which
is comparatively less-well explored in drug discovery.
.2. Proof of concept work
In order to establish the validity of the DOS strategy, the syn-
3
9
conditions provided derivative 42. Coupling with amine ‘carbonyl
capping’ building block 23 provided linear cyclization precursor 43
in a good yield. Pleasingly, 1,3-dipolar cycloaddition with copper
catalysis proceeded smoothly and with a high degree of regiose-
10
4
0
lectivity to furnish target macrocycle derivative 19 in a good yield.
2
The cycloaddition of 43 under ruthenium catalysis was investigated
in an attempt to generate the regioisomeric macrocycle containing
the 1,5-disubstituted triazole ring system. Although there was ev-
idence for the formation of the desired product, it could not be
isolated. Attention then turned towards the use of the alternative
‘carbonyl capping’ building block 44 in the DOS of compounds of
thesis of a representative member of each of the three different
general macrocyclic structural types 14e16 was targeted. We spe-
cifically chose compounds 19e21, which we envisaged could be
generated from building blocks 22e29 and 9 (Scheme 2).
the form 14. Compound 44 was readily prepared from L-proline by
In addition to demonstrating the feasibility of the DOS, these
specific compounds were selected as targets in order to probe both
the synthetic versatility of the DOS and also its’ capacity to furnish
macrocyles with certain interesting or desirable structural charac-
teristics. The target compounds covered a range of macrocyclic ring
sizes and included both cyclic and acyclic amine motifs, as well as
other functionalities and potential biomolecular interacting ele-
ments (e.g., hydrogen bond donors and acceptors). Each target
macrocycle also included a chiral centre, which we assumed could
be introduced through the use of chiral ‘carbonyl capping’ building
blocks (23, 26 and 28). If successful, this would demonstrate an-
other method to introduce stereochemical diversity into the mac-
rocycles through the building blocks (in addition to variation in the
scaffold-defining elements), which should facilitate the probing of
three-dimensional chemical space around the ring architectures.
Target compounds 19 and 20 contained aryl halide motifs, which
could potentially be further functionalised via various metal-
catalysed cross-coupling processes. Successful synthesis of 19
would thus demonstrate that a functional group handle for deri-
vitisation around the macrocyclic core could be introduced into
compounds of the general form 14. In the case of the representative
an analogous route to the preparation of 23 (see Experimental
Section). Coupling of 42 with 44 afforded acyclic precursor 45 in
a high yield. Pleasingly, subsequent macrocyclisation under copper-
catalysis again proceeded smoothly to furnish compound 46, an-
other macrocycle of the general form 14.
2.2.3. Synthesis of target compounds 20 and 21 from salicylaldehyde
25. It was anticipated that target macrocyclic compounds 20 and
21 could both be accessed from salicylaldehyde 25 (Scheme 5).
Attachment of the appropriate ‘hydroxyl capping’ building
blocks 27 or 29 (couple stage) proceeded smoothly to furnish
compounds 47 and 48. Reductive amination of 47 with ‘carbonyl
capping’ building block 26 furnished cyclization precursor 49. In
the par stage of the synthesis, the ring-closing metathesis of 49
with Hoveyda-Grubbs second generation catalyst was attempted,
but no product formation was observed. It was thought that the
lack of reactivity might be the result of deactivation of the me-
tathesis catalyst via coordination to the free amine of substrate 49.
Thus, metathesis was attempted with the addition of one equiva-
2
lent of p-toluenesulfonic acid hydrate (PTSA$H O) to the reaction
mixture in order to protonate the amine in situ. Pleasingly, this
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J.J. Ciardiello et al. / Tetrahedron xxx (2015) 1e12
5
Scheme 2. Proof-of-concept target macrocycles 19e21.
Scheme 3. Synthesis of building blocks.
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6
J.J. Ciardiello et al. / Tetrahedron xxx (2015) 1e12
Scheme 4. Synthesis of macrocycles 19 and 46.
allowed access to target macrorycle 20, albeit in a low yield (which
was attributed to incomplete consumption of the starting material,
despite the prolonged reaction time). Knoevenagel condensation of
compound 50 and subsequent coupling with ‘carbonyl capping’
building block 28 (the third couple stage) led to the formation of
macrocyclisation precursor 51. In the pair stage of the synthesis,
intramolecular ene-yne metathesis successfully afforded target
4
8 with ‘spacer’ building block 9 (the second couple stage) afforded
Scheme 5. Synthesis of macrocycles 20 and 21.
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J.J. Ciardiello et al. / Tetrahedron xxx (2015) 1e12
7
ꢀ
compound 21. The isolated yield of 21 was relatively low, which
again could be attributed to incomplete consumption of starting
material.
added at rt and the solution cooled to 0 C. Boc-anhydride (7.38 g,
ꢀ
33.8 mmol) was added and the solution stirred at 0 C for 2 h and
then at rt for 12 h. The THF was removed under reduced pressure
and resulting aqueous solution acidified with 10% HCl to pH 4. The
aqueous layer was extracted with EtOAc (3ꢁ100 mL). The organic
extracts were combined, washed with brine (80 mL) and dried
3
. Conclusions
Herein, we have described a new strategy for the expedient DOS
2 4
(Na SO ). The solvent was removed under reduced pressure to yield
2
0
of novel and structurally diverse macrocyclic compounds which are
based around a variety of distinct molecular scaffolds. The synthetic
approach is based around the use of aromatic starting materials
that bear an electrophilic carbonyl group and a nucleophilic hy-
droxyl group. These are designed to serve as ‘platforms’ onto which
different building blocks can be attached to afford a range of dis-
tinct acyclic precursors. Subsequent intramolecular cyclisation re-
actions would then furnish different macrocyclic compounds. It
was anticipated that the new DOS strategy would allow access to
macrocyclic compounds of the general structural forms 14e16. In
a proof-of-concept study, the synthesis of four different novel
macrocyclic compounds 19e21 and 46, including representative
examples of each of the different macrocyclic structural forms, was
achieved. Each of these four previously unreported compounds was
based around a distinct macrocyclic scaffold and contains func-
tional motifs that could potentially interact with biological targets.
These compounds are of significant interest from both a biological
and synthetic perspective and their successful generation provides
a validation of our new DOS strategy for the synthesis of structur-
ally diverse macrocycles. We anticipate that this approach holds
significant potential for library generation. It is step-efficient, pro-
ceeds from readily available starting materials and is modular in
nature, which should allow for concise access to a diverse range of
molecular scaffolds through variation in the building blocks at-
tached to the core aromatic unit. The DOS strategy also features the
use of three different macrocyclisation techniques, which allows for
potential access to different structural motifs embedded within the
macrocyclic architectures. Thus, we believe that this new DOS
strategy represents a valuable contribution to the repertoire of
strategies available for the synthesis of the biologically interesting
macrocycle compound class. Larger library synthesis endeavours
using this DOS algorithm are on-going. These, and the results of
subsequent biological screening studies (which we hope will lead
to the identification of novel antibacterial agents), will be reported
in due course.
the title compound as a white solid (6.14 g, 87%). [
a
]
D
þ29.7 (c 1.0,
ꢂ1
CHCl
3
). IR
n
max (neat)/cm : 3167 w br (OeH str), 1730 s (C]O str),
1
ꢀ
1653 s (C]O str). H NMR (500 MHz, DMSO-d
dd, J 12.9, 4.4 Hz, eCH e), 3.70 (1H, dt, J 12.9, 4.4 Hz, eCH
(1H, dd, J 12.9, 9.6 Hz, eCH ), 2.94e2.87 (1H, m, eCH e), 2.37e2.31
(1H, m, eCHe), 1.97e1.91 (1H, m, eCH e), 1.70e1.55 (2H, m,
6
, 120 C):
d
3.93 (1H,
2
2
e), 3.02
2
2
2
13
eCH
2
e), 1.46e1.35 (10H, m, eCH
2
e & CH
3
). C NMR (125 MHz,
ꢀ
DMSO-d
6
, 120 C):
d
174.5, 154.5, 79.2, 45.7, 44.0, 41.2, 28.6, 27.1,
þ
þ
þ
Na
24.2. HRMS (ESI ) m/z¼252.1212 [MþNa] found, C11
H
19
O
4
required 252.1206.
4.2.2. Synthesis of (S)-1-Boc-(prop-2-yn-1-yl)piperidine-3-
carboxamide (32). To a stirred solution of (S)-1-Boc-piperidine-3-
carboxylic acid (30) (1.00 g, 4.36 mmol) in EtOAc (35 mL), prop-
argylamine (31) (280
sultant solution cooled to 0 C. To this solution was added DIPEA
(1.5 mL, 8.80 mmol) and a solution of 50 wt. % T3P in EtOAc (3.4 mL,
m
L, 4.36 mmol) was added at rt and the re-
ꢀ
ꢀ
5.72 mmol). The solution was stirred for 30 min at 0 C before being
stirred at rt for 20 h. The reaction was quenched with H
and the aqueous layer extracted with EtOAc (2ꢁ5 mL). The organic
extracts were combined, dried (MgSO ) and the solvent removed
2
O (5 mL)
4
under reduced pressure to yield the title compound as a white solid
ꢂ1
(1.10 g, 95%). TLC R
f
¼0.12 (PE 30-40/EtOAc 7:3). IR
n
max (neat)/cm
:
3220 m (NeH str), 2967 m (CeH str), 2921 m (CeH str), 2860 m
(CeH str), 1684 s (C]O str), 1631 s (C]O str). H NMR (500 MHz,
1
CD
eCH
2.56 (1H, t, J 2.5 Hz, eCH), 2.33e2.27 (1H, m, eCHe), 1.92e1.88 (1H,
3
OD):
d
4.07 (1H, br d, J 11.5 Hz, eCH
2
e), 3.96 (1H, d, J 16.5 Hz,
2
e), 3.92 (2H, d, J 2.5 Hz, eCH
2
e), 3.00e2.70 (2H, m, eCH
2
e),
13
m, eCH
2
e), 1.72e1.62 (3H, m, eCH
2 3
e), 1.44 (9H, s, eCH ). C NMR
(125 MHz, CD
3
OD): 175.6, 156.4, 81.3, 80.6, 72.2, 45.7, 44.6, 44.1,
d
þ
þ
29.3, 28.9, 28.6, 25.5. HRMS (ESI ) m/z¼289.1536 [MþNa] found,
þ
C
14
H
22
O
3
N
2
Na required 289.1528.
4.2.3. Synthesis of (S)-N-(prop-2-yn-1-yl)piperidine-3-carboxamide
(23). (S)-1-Boc-(prop- eyn-1-yl)piperidine-3-carboxamide (32)
758 mg, 2.85 mmol) was dissolved in 4N HCl in 1,4-dioxane
2
(
4
4
. Experimental section
(26 mL) and stirred at rt for 2 h after which the solvent was re-
moved under reduced pressure to yield the crude product as
a brown solid. The crude product with triturated with chloroform
.1. General information
to yield the title compound as a white salt (444 mg, 77%). IR
(neat)/cm : 3276 m (NeH str), 2931 w (CeH str), 1650 m (C]O
n
max
ꢂ1
All reagents and solvents were purchased from commercial
1
sources and used without further purification unless otherwise
stated. All the experiments were carried out under a nitrogen at-
mosphere unless otherwise stated. Melting points were measured
using a B u€ chi B545 melting point apparatus and are uncorrected.
Thin layer chromatography (TLC) was performed on precoated
Merck silica gel GF254 plates. IR spectra were recorded on a Per-
kineElmer Spectrum One (FT-IR) spectrophotometer. Flash column
str). H NMR (500 MHz, CD
3.27e3.15 (3H, m, eCH e), 3.11e3.06 (1H, m, eCH
(1H, m, eCHe), 2.60 (1H, t, J 2.5 Hz, eCH), 2.02e1.89 (2H, m,
3
OD):
d
3.96 (2H, d, J 2.5 Hz, eCH
2
e),
2
2
e), 2.76e2.72
13
eCH
2 2 3
e), 1.82e1.73 (2H, m, eCH e). C NMR (125 MHz, CD OD):
d 174.2, 80.4, 72.3, 46.2, 45.1, 39.6, 29.4, 27.0, 21.2. HRMS (ESI ) m/
z¼167.1180 [MþH] found, C
þ
þ
þ
2
required 167.1179.
9
H15ON
1
chromatography was performed on silica gel (230e400 mesh). H
4.2.4. Synthesis of 3-(but-3-yn-1-yl) (S)-1-Boc-piperidine-3-
NMR and 13C NMR were recorded on a Bruker Avance 500 MHz
carboxylate (34). To a stirred solution of 30 (3.00 g, 13.1 mmol) in
ꢀ
instrument in CDCl
3
, (CD
3
)
2
CO and DMSO-d
6
. HRMS was recorded
CH
2
Cl
2
(30 mL), EDC (4.22 g, 22.0 mmol) was added at 0 C with
on a Micromass Q-TOF mass spectrometer or a Waters LCT Premier
Time of Flight mass spectrometer.
subsequent stirring for 40 min. To this solution was added DMAP
(348 mg, 2.86 mmol), DIPEA (9.12 mL, 52.3 mmol) and 3-butyn-1-ol
(33) (1.98 mL, 26.2 mmol). The solution was warmed to rt and
4
.2. Experimental details and characterization data
stirred for 17 h. The solvent was removed under reduced pressure
after which EtOAc (50 mL) was added. The organic phase was
4
.2.1. Synthesis of (S)-1-Boc-piperidine-3-carboxylic acid (30). (S)-
washed with 5% NaHCO
(30 mL) and then brine (30 mL). The organic extract was dried
(MgSO ) and the solvent removed under reduced pressure to yield
3
(2ꢁ50 mL), 5% citric acid (50 mL), H
2
O
Piperine-3-carboxylic acid (29) (4.00 g, 30.76 mmol) was dissolved
in THF (230 mL) and H O (230 mL). Na CO (12.0 g, 113 mmol) was
2
2
3
4
Please cite this article in press as: Ciardiello, J. J.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2015.10.061

8
J.J. Ciardiello et al. / Tetrahedron xxx (2015) 1e12
þ
the title compound as an amorphous, off-white solid (3.04 g, 83%).
35.7, 32.4). HRMS (ESI ) m/z¼346.0317 [MþH]þ found,
ꢀ
20
127 þ
TLC R
CHCl
f
¼0.37 (Hexane/EtOAc 4:1). Mp 72e74 C. [
a
]
D
þ28.1 (c¼1.0,
C H17NO I required 346.0304.
13 2
ꢂ1
3
). IR
n
max (neat)/cm : 3246 s (CeH str), 1726 s (C]O str),
1
ꢀ
1673 s (C]O str). H NMR (500 MHz, DMSO-d
6
, 120 C):
d
4.15 (2H,
e), 3.68
e), 3.09 (1H, dd, J 13.2, 9.5 Hz, eCH e),
e, eCHe &
e),
). C NMR (125 MHz, DMSO-d
172.8, 154.5, 81.0, 79.2, 72.1, 62.4, 45.9, 44.0, 41.3, 28.6,
4.2.8. Synthesis of 5-azidopentyl tosylate (38). To a stirred solution
of 5-azidopentyl alcohol (39) (4.44 g, 34.3 mmol) in CH Cl
(213 mL) was added TEA (4.78 mL) and TsCl (9.82 g, 51.5 mmol) at
td, J 6.6, 1.6 Hz, eCH e), 3.93 (1H, dd, J 13.2, 4.1 Hz, eCH
2
2
2
2
(
1H, dt, J 13.2, 4.1 Hz, eCH
2
2
ꢀ
2
.98e2.92 (1H, m, eCH
2
e), 2.59e2.43 (4H, m, eCH
2
0 C. The solution was allowed to warm to rt and stirred for 19 h.
eCH), 1.99e1.91 (1H, m, eCH
2
e), 1.72e1.61 (2H, m, eCH
2
CH
(2ꢁ100 mL) and brine (50 mL). The organic extract was dried
(MgSO ) and the solvent removed under reduced pressure. The
2 2 2
Cl (100 mL) was added and the organic layer washed with H O
13
1
.47e1.37 (10H, m, eCH e & eCH
2
3
6
,
ꢀ
120 C):
d
4
þ
þ
2
6.9, 24.1, 18.1. HRMS (ESI ) m/z¼304.1510 [MþNa] found,
crude product purified by flash column chromatography, eluting
with a gradient from 5% to 20% EtOAc in hexane to yield the title
þ
C
15
H
23NO
4
Na required 304.1519.
compound as a colourless oil (6.59 g, 68%). TLC R
f
¼0.19 (Hexane/
ꢂ1
4
.2.5. Synthesis of but-3-yn-1-yl (S)-piperidine-3-carboxylate hy-
drochloride (28). 34 (140 mg, 498 mol) was dissolved in 4N HCl in
dioxane (3 mL) and stirred for 3 h, after which the solvent was
removed under reduced pressure. To the residue was added H
EtOAc 9:1). IR
str), 2091 s (N
O str), 1176 s (S]O str). H NMR (400 MHz, CDCl
6.4 Hz, ArH), 7.33 (2H, d, J 6.4 Hz, ArH), 4.01 (2H, t, J 6.4 Hz, eCH
3.21 (2H, t, J¼6.8 Hz, eCH e), 2.42 (3H, s, eCH ), 1.69e1.62 (2H, m,
eCH e), 1.56e1.48 (2H, m, eCH e), 1.41e1.34 (2H, m, eCH
NMR (100 MHz, CDCl ): 144.8, 132.9, 129.8, 127.8, 70.1, 51.0, 28.3,
n
max (neat)/cm : 2937 m (CeH str), 2871 m (CeH
m
3
str), 1596 m (C]C str), 1451 m (C]C str), 1350 s (S]
1
3
):
d
7.77 (2H, d, J
e),
2
O
2
(
7 mL) and the solution freeze dried to yield the title compound as
2
3
ꢂ1
13
a brown oil (100 mg, 92%). IR
2
1
dd, J 12.3, 3.4 Hz, eCH
2
2
eCH
NMR (125 MHz, DMSO-d
4
found, C10
n
max (neat)/cm : 3282 w (NeH str),
2
2
2
e).
C
1
944 m (CeH str), 1726 s (C]O str). H NMR (500 MHz, DMSO-d
6
,
3
d
ꢀ
þ
þ
20 C):
d
9.53 (2H, br, -NH-), 4.22e4.15 (2H, m, eCH
e), 3.17 (1H, dt, J 12.6, 3.8 Hz, eCH
e), 2.87e2.82 (1H, m, eCH e), 2.67 (1H, t, J
.8 Hz, eCH), 2.54 (2H, td, J 6.6, 2.8 Hz, eCH e), 2.08e2.01 (1H, m,
2
e), 3.34 (1H,
28.1, 22.6, 21.6. HRMS (ESI ) m/z¼306.0895 [MþNa] found,
þ
2
2
e),
C
12
H
17
O
3
N
3
SNa required 306.0883.
.97e2.92 (1H, m, eCH
2
2
2
4.2.9. Synthesis of ethyl 3-bromo-5-hydroxybenzoate (40). To a stir-
red solution of 3-bromo-5-hydroxy benzoic acid (22) (5.19 g,
13
2
e), 1.91e1.79 (2H, m, eCH
2
ꢀ
e), 1.69e1.60 (1H, m, eCH
2
e).
C
6
, 120 C):
d
¼171.6, 81.0, 72.4, 62.8, 44.3,
23.9 mmol) in EtOH (50 mL), H
solution refluxed at 70 C for 72 h. The solvent was removed under
2
SO
4
(1 mL) was added at rt and the
þ
þ
ꢀ
3.3, 38.4, 25.1, 21.2, 18.6. HRMS (ESI ) m/z¼182.1183 [MþH]
þ
H16NO
2
required 182.1181.
reduced pressure and to it added EtOAc (100 mL). The organic
phase was washed with satd NaHCO
The organic extract was dried (MgSO
under reduced pressure to yield the title compound as an orange
3
(2ꢁ50 mL) and brine (50 mL).
4
.2.6. Synthesis of but-3-en-1-yl Boc-4-iodo-
L
-phenylalanine
4
) and the solvent removed
(
37). To a stirred solution of Boc-4-iodo-L-phenylalanine (2.00 g,
ꢀ
ꢀ
5
.11 mmol) in CH
2
Cl
2
(20 mL) was added EDC (2.34 g, 12.2 mmol),
solid (5.48 g, 94%). Mp 99e101 C (lit. value 96 C). TLC R
f
¼0.25 (PE
ꢀ
ꢂ1
DMAP (183 mg, 1.50 mmol) and 3-buten-1-ol (1.20 mL) at 0 C. The
solution was warmed to rt and stirred for 19 h. The solution was
30-40/EtOAc 9:1). IR
n
max (neat)/cm : 3392 m br (OeH str), 3094
w (CeH str), 2972 w (CeH str), 2926 w (CeH str), 1691 s (C]O str),
diluted with CH
NaHCO (50 mL), H
extract was dried (MgSO
2
Cl
2
(50 mL) and the organic phase washed with 5%
O (30 mL) and then brine (30 mL). The organic
) and the crude product purified by flash
1603 m (C]C str), 1588 m (C]C str), 1480 m (C]C str),1461 m (C]
1
3
2
C str), 1439 m (C]C str). H NMR (400 MHz, CDCl
3
):
d
7.72 (1H, d, J
4
1.2 Hz, ArH), 7.53 (1H, dd, J 2.4, 1.2 Hz, ArH), 7.22 (1H, dd, J 2.4,
2.0 Hz, ArH), 4.37 (2H, q, J 7.2 Hz, eCH e), 1.38 (3H, t, J 7.2 Hz,
column chromatography eluting with 50% EtOAc in hexane to yield
the title compound as crystalline, yellow solid (1.70 g, 75%).
2
1
3
eCH
3
). C NMR (100 MHz, CDCl
3
):
d
165.7,156.6,132.9,124.8, 123.3,
122.8, 115.5, 61.8, 14.2. HRMS (ESI ) m/z¼266.9634 [MþNa] found,
ꢀ
20
þ
þ
Mp¼75e77 C. TLC R
f
¼0.70 (Hexane/EtOAc 1:1). [
a
]
D
þ26.1 (c 1.0,
ꢂ1
þ
CHCl
3
). IR
n
max (neat)/cm : 3373 m (NeH str), 2972 m (CeH str),
C
9
H
9
O
3
BrNa required 266.9627.
41
1
726 s (C]O str), 1687 s (C]O str), 1514 s (C]C str), 1485 m (C]C
These data are consistent with those previously reported.
1
str),1443 m (C]C str). H NMR (500 MHz, DMSO-d
6
):
.2 Hz, ArH), 7.27 (1H, t, J 7.9 Hz, -NH-), 7.04 (2H, d, J 8.2 Hz, ArH),
.71 (1H, ddq, J 17.4, 10.4, 6.7 Hz, eCHCH ), 5.07 (1H, d, J 17.1 Hz,
), 5.03 (1H, d, J 10.4 Hz, eCH ), 4.14e4.00 (3H, m, eCH
eCH), 2.92 (1H, dd, J 13.7, 5.5 Hz, eCH e), 2.79 (1H, dd, J 13.7,
.8 Hz, eCH e), 2.25 (2H, q, J 7.3 Hz, eCH
NMR (125 MHz, DMSO-d
d 7.62 (2H, d, J
8
5
eCH
4.2.10. Synthesis of ethyl 3-((5-azidopentyl)oxy)-5-bromobenzoate
2
(41). A solution of 38 (4.65 g, 16.4 mmol) and LiBr (4.27 g,
ꢀ
2
2
2
&
49.2 mmol) in acetone (53 mL) was refluxed at 70 C for 18 h. The
2
solution was filtered to remove the precipitate yielding a solution of
the corresponding bromide 24 in acetone (53 mL). Ethyl 3-bromo-
5-hydroxybenzoate (40) (1.34 g, 5.47 mmol), KI (83 mg, 500 mmol),
13
9
2
2 3
e), 1.31 (9H, s, eCH ). C
6
):
d
¼172.4, 155.8, 137.8, 137.4, 134.7, 132.0,
þ
1
17.7, 92.7, 78.9, 64.0, 55.5, 36.4, 32.9, 28.5. HRMS (ESI ) m/
18-crown-6 (66 mg, 250
added to the solution of 24 at rt. The mixture was refluxed at 70 C
m
mol) and K
2
CO
3
(2.27 g, 16.4 mmol) were
þ
127
þ
ꢀ
z¼468.0637 [MþNa] found, C18
H24NO
4
INa required 468.0642.
for 42 h. The solvent was then removed under reduced pressure,
4
.2.7. Synthesis of but-3-en-1-yl 4-iodo-
ride (26). 37 (1.59 g, 3.57 mmol) was dissolved in 4N HCl in dioxane
24 mL) and stirred for 3 h, after which the solvent was removed
under reduced pressure. To the residue was added H O (25 mL) and
L
-phenylalanine hydrochlo-
EtOAc (60 mL) added and the organic layer washed with H
(60 mL). The aqueous layer was separated and extracted with EtOAc
(60 mL). The organic extracts were combined, washed with H
(60 mL) and brine (30 mL), dried (MgSO ) and the solvent removed
2
O
(
2
O
2
4
the solution freeze dried to yield the title compound as a crystalline
under reduced pressure. The crude product was purified by flash
column chromatography, eluting with a gradient from 2% to 4%
EtOAc in petroleum ether 30e40 to yield the title compound as an
ꢀ
20
off-white solid (1.36 g, 100%). Mp 145e147 C. [
a
]
D
þ17.3 (c 1.0,
ꢂ1
CHCl
3
). IR
nmax (neat)/cm : 3147 w (NeH str), 2845 m (CeH str),
1
1
738 s (C]O str), 1641 w (C]C str), 1606 w (C]C str). H NMR
500 MHz, DMSO-d ): 7.69 (2H, d, J 8.2 Hz, ArH), 7.05 (2H, d, J
.5 Hz, ArH), 5.64 (1H, ddq, J 17.0, 10.2, 6.5 Hz, eCHCH ), 5.08e5.01
2H, m, eCH ), 4.23 (1H, dd, J 7.5, 6.1 Hz, eCHe), 4.10 (2H, t, J 6.1 Hz,
e), 3.10 (1H, dd, J 14.0, 6.1 Hz, eCH e), 3.00 (1H, dd, J 14.0,
e), 2.24 (2H, q, J 6.8 Hz, eCH
169.1, 137.7, 134.6, 134.3, 132.1, 117.8, 93.8, 65.1, 53.2,
orange oil (1.94 g, 98%). TLC R
(neat)/cm : 2932 m (CeH str), 2086 s (N
f
¼0.29 (Hexane/EtOAc 19:1). IR
n
max
ꢂ1
(
6
d
3
str), 1719 s (C]O str),
8
2
1593 m (C]C str), 1570 m (C]C str), 1439 m (C]C str), 1391 w (C]
1
(
2
C str), 1360 w (C]C str). H NMR (500 MHz, CDCl
1.5 Hz, ArH), 7.47 (1H, dd, J 2.5, 1.5 Hz, ArH), 7.21 (1H, s, ArH), 4.35
(2H, q, J 7.0 Hz, eCH e), 3.99 (2H, t, J 6.0 Hz, eCH e), 3.31 (2H, t, J
7.0 Hz, eCH e), 1.84e1.79 (2H, m, eCH e), 1.70e1.64 (2H, m,
3
): d 7.74 (1H, t, J
eCH
2
2
13
7.5 Hz, eCH
2
2
e). C NMR (125 MHz,
2
2
DMSO-d
6
:
d
2
2
Please cite this article in press as: Ciardiello, J. J.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2015.10.061

J.J. Ciardiello et al. / Tetrahedron xxx (2015) 1e12
9
eCH
2
e), 1.59e1.52 (2H, m, eCH
2
e), 1.38 (3H, t, J 7.0 Hz, eCH
3
). 13
C
7.09 (1H, s, ArH), 6.78 (1H, s, ArH), 4.78 (1H, d, J 14.8 Hz, eCH
4.57e4.32 (3H, m, eCH e), 4.04e3.92 (3H, m, eCH
13.6 Hz, eCH e), 3.13 (1H, dd, J 13.6, 10.0 Hz, eCH
(1H, m, eCH e), 2.47e2.42 (1H, m, eCHe), 2.13e1.53 (6H, m,
eCH e), 1.52e1.47 (2H, m, eCH
NMR (100 MHz, CD OD): 173.4, 168.4, 159.1, 137.8, 123.3, 122.3,
116.2, 112.8, 67.3, 50.1, 49.5, 43.5, 42.2, 33.5, 29.1, 28.2, 27.9, 24.0,
2
e),
NMR (125 MHz, CDCl
3
):
d
165.6, 160.0, 133.5, 125.2, 123.0, 122.8,
2
2
e), 3.72 (1H, d, J
e), 2.88e2.81
þ
1
14.4, 68.6, 61.9, 51.7, 29.0, 23.7, 14.7. HRMS (ESI ) m/z¼378.0430
2
2
þ
þ
[MþNa] found, C14
18
H O
3
N
3
BrNa required 378.0424.
2
13
2
2
e), 1.38e1.12 (2H, m, eCH2-).
C
4.2.11. Synthesis of 3-((5-azidopentyl)oxy)-5-bromobenzoic acid
3
d
(
42). To a stirred solution of ethyl 3-((5-azidopentyl)oxy)-5-
þ
þ
þ
Br
bromobenzoate (41) (1.57 g, 4.41 mmol) in EtOH (13.2 mL) and
THF (4.4 mL) was added a solution of LiOH (231 mg, 5.50 mmol) in
23.1. HRMS (ESI ) m/z¼476.1306 [MþH] found, C21
H
27
O
3
N
5
required 476.1292.
2
H O (4.4 mL) at rt. The solution was stirred for 16 h and then
acidified with 10% HCl to pH 3. The aqueous layer was extracted
with EtOAc (2ꢁ80 mL) and the organic extracts were combined,
4.2.14. Synthesis of (S)-N-(prop-2-yn-1-yl)proline carboxamide hy-
drochloride (44). To stirred solution of -proline (5.00 g,
43.4 mmol) in THF (325 mL) and H O (325 mL), Na
a
L
washed with H
2
O (50 mL), brine (50 mL) and dried (MgSO
4
). The
2
2
CO
3
(17.3 g,
ꢀ
solvent was removed under reduced pressure to yield the title
162 mmol) was added at rt and the resultant solution cooled to 0 C.
Following the addition of Boc-anhydride (10.4 g, 47.8 mmol), the
ꢀ
compound as an orange solid (1.30 g, 90%). Mp 102e104 C. IR
n
max
ꢂ1
ꢀ
(
neat)/cm : 2942 w br (OeH str), 2081 s (N
3
str), 1686 s (C]O str),
solution was stirred at 0 C for 2 h and then at rt for 18 h. The THF
1
590 m (C]C str), 1573 m (C]C str), 1461 m (C]C str), 1432 m (C]
was removed under reduced pressure and the resulting aqueous
solution acidified with 1M HCl to pH 4. The aqueous layer was
extracted with EtOAc (3ꢁ50 mL) and the organic extracts were
1
C str), 1418 m (C]C str), 1398 m (C]C str). H NMR (400 MHz,
CDCl ): 7.81 (1H, t, J 1.6 Hz, ArH), 7.53e7.51 (1H, m, ArH), 7.27 (1H,
dd, J 1.8, 1.6 Hz, ArH), 4.00 (2H, t, J 6.2 Hz, eCH e), 3.30 (2H, t, J
e), 1.71e1.63 (2H, m,
e). C NMR (100 MHz, CDCl ):
3
d
2
combined and dried (Na
reduced pressure to yield N-Boc-
N-Boc- -proline (2.00 g, 9.29 mmol) in EtOAc (70 mL), propargyl-
2 4
SO ). The solvent was removed under
6
eCH
.4 Hz, eCH
2
e), 1.87e1.80 (2H, m, eCH
2
L-proline. To a stirred solution of
13
2
e), 1.61e1.57 (2H, m, eCH
2
3
L
d
169.3, 159.7, 131.5, 125.4, 123.4, 122.8, 114.5, 68.2, 51.3, 28.6, 23.3.
amine (31) (600
m
L, 9.34 mmol) was added at rt and then cooled to
þ
þ
þ
ꢀ
HRMS (ESI ) m/z¼350.0112 [MþNa] found, C12
H
14
O
3
N
3
BrNa re-
0
C. To this solution was added DIPEA (3.2 mL, 18.8 mmol) and
quired 350.0111.
a solution of 50 wt. % T3P in EtOAc (7.25 mL, 12.2 mmol). The so-
lution was stirred at 0 C for 30 min before being stirred at rt for
ꢀ
4
.2.12. Synthesis of azido-alkyne (43). (S)-N-(prop-2-yn-1-yl)pi-
peridine-3-carboxamide (23) (31 mg, 150 mol) and 3-((5-
azidopentyl)oxy)-5-bromobenzoic acid (42) (50 mg, 150
20 h. The reaction was quenched with H
was added and the organic layer separated and washed with 5%
NaHCO (50 mL), 5% citric acid (50 mL) and brine (50 mL). The
organic extract was dried (MgSO ) and the solvent removed under
reduced pressure to yield (S)-1-Boc-(prop-2-yn-1-yl)proline car-
boxamide. (S)-1-Boc-(prop-2-yn-1-yl)proline carboxamide
(734 mg, 2.80 mmol) was dissolved in 4N HCl in 1,4-dioxane
(26 mL) and stirred at rt for 2 h after which the solvent was re-
moved under reduced pressure to yield the crude product as
a brown solid. The crude product with triturated with chloroform
2
O (50 mL), EtOAc (50 mL)
m
m
ꢀ
mol)
3
were dissolved in EtOAc (1.2 mL) at rt and then cooled to 0 C. To
this solution was added DIPEA (100
4
mL, 600
mmol) and a solution of
5
0
0 wt. % T3P in EtOAc (120
mL, 195
mmol). The solution was stirred at
ꢀ
C for 30 min before being stirred at rt for 20 h. The reaction was
O (20 mL) and EtOAc (20 mL) was added. The
organic layer was separated and washed with 5% citric acid
2ꢁ20 mL), 5% NaHCO (20 mL) and then brine (20 mL). The organic
extract was dried (MgSO ) and the solvent removed under reduced
quenched with H
2
(
3
4
to yield the title compound as a white salt (470 mg, 47% over three
ꢂ1
pressure. The crude product was purified with flash column chro-
matography, eluting with 60% EtOAc in petroleum ether 30e40 to
yield the title compound as a colourless oil (49 mg, 69%). TLC
steps). IR
n
max (neat)/cm : 3235 m (NeH str), 2911 m (CeH str),
1
1687 m (C]O str). H NMR (400 MHz, CD
eCHe), 3.93 (2H, d, J 2.4 Hz, eCH e), 3.31e3.22 (2H, m, eCH
2.56 (1H, t, J 2.4 Hz, eCH), 2.35e2.30 (1H, m, eCH e), 1.97e1.87
3
OD):
d
4.14 (1H, t, J 7.6 Hz,
2
2
e),
ꢂ1
R
f
¼0.25 (PE 30-40/EtOAc 4:6). IR
n
max (neat)/cm : 2937 w (CeH
2
13
str), 2865 w (CeH str), 2096 s (N
3
str), 1623 m (C]O str), 1563 m
(3H, m, eCH
2
e). C NMR (100 MHz, CD
3
OD):
d
169.2, 79.9, 72.8,
1
þ
þ
(
C]C str), 1464 m (C]C str), 1434 m (C]C str). H NMR (500 MHz,
61.1, 47.3, 30.8, 29.8, 25.0. HRMS (ESI ) m/z¼153.1021 [MþH]
þ
DMSO-d
4
eCH
3
6
):
d
7.26 (1H, s, ArH), 7.02 (1H, s, ArH), 6.73 (1H, s, ArH),
e), 4.06 (2H, t, J 7.0 Hz, eCH e), 3.93 (2H, s,
e), 3.64e3.57 (1H, m, eCH e), 3.34 (2H, t, J 7.0 Hz, eCH e),
e), 2.55e2.36 (2H, m, eCHe & eCH),
found, C
8
H13ON
2
required 153.1022.
.57e4.14 (1H, m, eCH
2
2
2
2
2
4.2.15. Synthesis of azido-alkyne (45). (S)-N-(prop-2-yn-1-yl)pro-
line carboxamide hydrochloride (44) (28 mg, 150 mol) and 3-((5-
azidopentyl)oxy)-5-bromobenzoic acid (42) (50 mg, 150
.18e3.03 (2H, m, eCH
.00e1.72 (4H, m, eCH
)eExists as a mixture of rotamers:
2
m
13
2
2
e), 1.61e1.21 (6H, m, eCH
2
e). C NMR
174.1,
m
mol)
ꢀ
(
125 MHz, DMSO-d
6
d
were dissolved in EtOAc (1.2 mL) at rt and then cooled to 0 C. To
1
5
70.6, 161.5, 139.8, 124.0, 122.6, 120.1, 113.0, 80.5, 72.2, 69.5, 52.4,
this solution was added DIPEA (100
m
L, 600
mmol) and a solution of
þ
0.8, 45.6, 44.1, 43.6, 29.7, 29.4, 28.7, 26.1, 25.0. HRMS (ESI ) m/
50 wt. % T3P in EtOAc (120
0 C for 30 min before being stirred at rt for 20 h. The reaction was
m
L,195
m
mol). The solution was stirred at
þ
þ
ꢀ
z¼476.1313 [MþH] found, C21
27
H O
3
N
5
Br required 476.1297.
quenched with H
organic layer was separated and washed with 5% citric acid
(2ꢁ20 mL), 5% NaHCO (20 mL) and then brine (20 mL). The organic
extract was dried (MgSO ) and the solvent removed under reduced
2
O (20 mL) and EtOAc (20 mL) was added. The
4.2.13. Synthesis of macrocycle (19). To a solution of 43 (17 mg,
3
6.0
m
mol) in THF (20 mL) was added CuI (13.6 mg, 71.0
m
mol) and
3
ꢀ
DIPEA (18
mL, 107
mmol) at rt. The solution was refluxed at 70 C for
4
4
4 h. The solvent was removed under reduced pressure and the
pressure. The crude product was purified with flash column chro-
matography, eluting with 60% EtOAc in petroleum ether 30e40 to
crude product purified by flash column chromatography, eluting
with 5% MeOH in EtOAc to yield the title compound as a colourless
yield the title compound as a colourless oil (65 mg, 93%). TLC
ꢂ1
oil (14.3 mg, 30.0
m
mol, 83%). TLC R
f
¼0.15 (EtOAc/MeOH 19:1). IR
R
f
¼0.25 (PE 30-40/EtOAc 4:6). IR
n
max (neat)/cm : 3291 m (NeH
ꢂ1
n
max (neat)/cm : 2942 w (CeH str), 2865 w (CeH str), 1661 m (C]
3
str), 2937 w (CeH str), 2876 w (CeH str), 2096 s (N str), 1661 m
O str), 1630 m (C]O str), 1603 m (C]C str), 1560 m (C]C str), 1467
m (C]C str), 1449 m (C]C str), 1436 m (C]C str). H NMR
(C]O str), 1621 m (C]O str), 1568 m (C]C str), 1454 m (C]C str),
1
1
1431 m (C]C str), 1413 m (C]C str). H NMR (500 MHz, DMSO-d
6
,
ꢀ
(
400 MHz, CD
3
OD):
d
7.80 (1H, s, eCHe), 7.15 (1H, t, J 2.0 Hz, ArH),
120 C):
d
7.20 (1H, s, ArH), 7.10 (1H, s, ArH), 6.68 (1H, s, ArH), 4.41
Please cite this article in press as: Ciardiello, J. J.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2015.10.061

10
J.J. Ciardiello et al. / Tetrahedron xxx (2015) 1e12
(
3
1H, br, eCHe), 4.06 (2H, m, eCH
.58e3.46 (2H, m, eCH e), 3.34 (2H, t, J 6.8 Hz, eCH
J 2.5 Hz, eCH), 2.20e2.16 (1H, m, eCH e), 1.94e1.83 (3H, m,
eCH e), 1.81e1.75 (2H, m, eCH e), 1.69e1.62 (2H, m, eCH
2
e), 3.95e3.82 (2H, m, eCH
2
e),
J 6.6, 1.4 Hz, eCH
2
e). 13C NMR (100 MHz, CDCl
3
):
d
189.9, 161.3,
þ
2
2
e), 2.79 (1H, t,
135.9, 134.0, 128.2, 125.0, 120.7, 117.6, 112.5, 67.7, 33.5. HRMS (ESI ):
m/z¼199.0723 [MþNa]þ found, C11
H
12
O
Na required 199.0730.
þ
2
2
2
2
2
e),
13
ꢀ
1
.57e1.52 (2H, m, eCH
2
e). C NMR (125 MHz, DMSO-d
6
, 120 C):
4.2.19. Synthesis of but-3-en-1-yl (S)-2-((2-(allyloxy)benzyl)amino)-
d
171.8, 167.6, 159.7, 140.3, 122.4, 122.3, 118.9, 113.1, 81.4, 73.5, 68.4,
3-(4-iodophenyl)propanoate (49). To a stirred solution of 47 (50 mg,
þ
6
1.2, 51.0, 47.2, 30.1, 28.5, 25.4, 23.2. HRMS (ESI ) m/z¼462.1137
308
mmol) and 26 (130 mg, 341
mmol) in THF (3 mL) was added
þ
þ
[MþH] found, C20
H
25
O
3
N
5
Br required 462.1135.
NaBH(OAc)
3
(290 mg, 1.37 mmol) at rt, after which the solution was
stirred for 18 h. The reaction was quenched with 1M NaOH (10 mL)
and extracted with EtOAc (3ꢁ20 mL). The organic layers were
combined and washed with brine (20 mL). The organic extract was
4
8
.2.16. Synthesis of macrocycle (46). To a solution of 45 (40.0 mg,
7.0
m
mol) in THF (40 mL) was added CuI (28.4 mg, 150
m
mol) and
ꢀ
DIPEA (42.0
mL, 240
mmol) at rt. The solution was refluxed at 70 C
4
dried (MgSO ) and the crude product purified by flash column
for 20 h. The solvent was removed under reduced pressure and the
crude product purified by flash column chromatography, eluting
with 5% MeOH in EtOAc to yield the title compound as a colourless
chromatography, eluting with a gradient from 10% to 15% EtOAc in
petroleum ether 30e40 to yield the title compound as a pale yellow
2
0
oil (73.5 mg, 49%). TLC R
1.0, CHCl ). IR
f
¼0.47 (PE 30-40/EtOAc 7:3). [
a]
D
þ6.6 (c
ꢂ1
oil (34.7 mg, 87%). TLC R
cm : 2932 w (CeH str), 2876 w (CeH str), 1618 m (C]O str), 1601
f
¼0.15 (EtOAc/MeOH 19:1). IR
n
max (neat)/
3
n
max (neat)/cm : 2960 w (CeH str), 2861 w (CeH
ꢂ1
str), 1728 s (C]O str), 1643 w (C]C str), 1602 w (C]C str), 1588 w
1
m (C]C str),1560 m (C]C str),1451 m (C]C str),1436 m (C]C str),
3
(C]C str). H NMR (500 MHz, CDCl ): d 7.55 (2H, d, J 8.5 Hz, ArH),
1
1
413 m (C]C str). H NMR (400 MHz, CD
3
OD):
d
7.76 (1H, s, eCHe),
7.19 (1H, td, J 7.6, 1.8 Hz, ArH), 7.13 (1H, dd, J 7.3, 1.8 Hz, ArH),
6.89e6.86 (3H, m, ArH), 6.77 (1H, d, J 7.6 Hz, ArH), 5.95 (1H, ddt, J
7
1
eCH
eCH
.16 (1H, s, ArH), 7.13 (1H, s, ArH), 6.67 (1H, s, ArH), 4.57 (1H, d, J
5.2 Hz, eCH e), 4.44e4.50 (2H, m, eCH e), 4.29e4.23 (2H, m,
e & eCHe), 3.90e3.88 (2H, m, eCH e), 3.78e3.67 (2H, m,
e), 2.22e1.94 (6H, m, eCH e), 1.81e1.75 (2H, m, eCH e),
e). C NMR (100 MHz, CD OD): 174.3,
70.1, 160.8, 146.2, 140.4, 124.6, 124.4, 123.0, 117.7, 114.5, 68.3, 64.4,
2
2
17.4, 10.4, 4.9 Hz, eCHCH
eCHCH ), 5.35 (1H, dq, J 17.1, 1.5 Hz, eCH
1.5 Hz, eCH ), 5.09e5.04 (2H, m, eCH ), 4.48e4.38 (2H, m, eCH
4.06 (2H, t, J 6.7 Hz, eCH e), 3.85 (1H, d, J 13.4 Hz, eCH e), 3.65
(1H, d, J 13.4 Hz, eCH e), 3.47 (1H, dd, J 7.6, 6.1 Hz, eCHe), 2.90 (1H,
dd, J 13.7, 6.1 Hz, eCH e), 2.83 (1H, dd, J 13.7, 7.6 Hz, eCH e), 2.30
(2H, qdd, J 6.7, 1.5, 1.2 Hz, eCH e). C NMR (125 MHz, CDCl ):
174.1, 156.6, 137.4, 137.1, 133.8, 133.2, 131.2, 129.9, 128.3, 127.7,
120.5, 117.3, 117.0, 111.4, 91.9, 68.5, 63.7, 61.7, 47.6, 39.0, 33.0. HRMS
2
), 5.68 (1H, ddt, J 17.1, 10.4, 6.7 Hz,
), 5.24 (1H, dq, J 10.7,
e),
2
2
2
2
2
2
2
2
2
2
13
1.42e1.25 (2H, m, eCH
2
3
d
2
2
1
2
þ
5
0.4, 47.9, 35.8, 33.1, 29.1, 27.8, 23.2, 22.4. HRMS (ESI ) m/
2
2
þ
þ
13
z¼462.1145 [MþH] found, C20
25
H O
3
N
5
Br required 462.1135.
2
3
d
4.2.17. Synthesis of 2-(allyloxy)benzaldehyde (47). To a stirred so-
þ
þ
127
þ
lution of salicylaldehyde (20.0 g,164 mmol) in acetonitrile (200 mL)
was added allylbromide (27) (29.0 mL, 333 mmol), KI (544 mg,
(ESI ) m/z¼492.1024 [MþH] found, C23
3
H27NO INa required
492.1030.
3
.28 mmol), 18-crown-6 (432 mg, 1.64 mmol) and K
2
CO
3
(66.0 g,
ꢀ
478 mmol) at rt after which the solution was refluxed at 75 C for
4.2.20. Synthesis of macrocycle (20). To a degassed solution of 49
(34.3 mg, 73.9 mol) in CH Cl (125 mL) was added PTSA.H
(15.2 mg, 79.9
subsequently refluxed at 55 C for 1 h after which was added
HoveydaeGrubbs second generation catalyst (4.5 mg, 7.21 mmol)
1
8 h. The K
reduced pressure. H
extracted with EtOAc (2ꢁ100 mL). The organic layers were com-
bined, washed with brine (50 mL), dried (Na SO ) and the solvent
removed under reduced pressure to yield the title compound as an
2
CO
3
was filtered off and the solvent removed under
m
2
2
2
O
2
O (100 mL) was added and the aqueous layer
m
mol) under an argon atmosphere. The reaction was
ꢀ
2
4
followed by stirring for 72 h. The solution was degassed a second
orange oil (24.2 g, 84%). TLC R
f
¼0.28 (Hexane/EtOAc 19:1). IR
n
max
time and to the solution was added HoveydaeGrubbs second
ꢂ1
(
neat)/cm : 2861 w (CeH str), 1681 s (C]O str), 1598 s (C]C str),
generation catalyst (6.3 mg, 7.39
m
mol) under an argon atmosphere.
1
ꢀ
1483 m (C]C str), 1457 m (C]C str). H NMR (400 MHz, CDCl
3
):
The reaction was subsequently reluxed at 55 C for 16 h. The re-
d
10.51 (1H, s, eCHO), 7.80 (2H, dd, J 7.5,1.7 Hz, ArH), 7.50 (1H, ddd, J
.5, 7.5, 2.0 Hz, ArH), 6.99 (1H, t, J 7.5 Hz, ArH), 6.95 (1H, d, J 8.5 Hz,
action was quenched with NaHCO
moved under reduced pressure. The aqueous layer was extracted
with CH Cl , after which the organic phases were combined,
washed with brine (30 mL) and dried (MgSO ). The crude product
was purified by flash column chromatography, eluting with 30%
EtOAc in petroleum ether 30e40 to yield the title compound as
3
(30 mL) and the solvent re-
8
ArH), 6.10e6.00 (1H, m, eCHCH
.31 (1H, dq, J 10.6,1.4 Hz, eCH
), 4.63 (1H, dt, J¼5.1,1.4 Hz, eCH
189.7, 160.9, 135.9, 132.4, 128.4, 125.1,
2
), 5.43 (1H, dq, J 17.4, 1.7 Hz, eCH
2
),
2
2
5
2
2
e).
4
1
3
C NMR (125 MHz, CDCl
3
):
d
þ
þ
1
C
20.9, 118.1, 112.9, 69.2. HRMS (ESI ) m/z¼163.0751 [MþH] found,
þ
10 11
H O
2
required 163.0754.
a colourless oil (9.0 mg, 26%). TLC R
f
¼0.25 (PE 30-40/EtOAc 7:3).
2
0
ꢂ1
[
a
]
D
þ37.1 (c 1.0, CHCl
3
). IR
n
max (neat)/cm : 2921 w (CeH str),
1
4
.2.18. Synthesis of 2-(but-3-en-1-yloxy)benzaldehyde (48). To
1728 s (C]O str), 1600 w (C]C str), 1586 w (C]C str). H NMR
(500 MHz, CDCl ): 7.56 (2H, d, J 8.2 Hz, ArH), 7.23 (1H, td, J 7.9,
a stirred solution of salicylaldehyde (1.00 g, 8.19 mmol) in aceto-
3
d
nitrile (10 mL) was added 4-bromobut-1-ene (29) (2.90 mL,
1.5 Hz, ArH), 7.11 (1H, dd, J 7.3, 1.8 Hz, ArH), 6.93e6.89 (2H, m, ArH),
6.87 (2H, d, J 8.2 Hz, ArH), 5.98e5.91 (1H, m, eCHCHe), 5.79e5.73
16.2 mmol), KI (136 mg, 819 mmol), 18-crown-6 (108 mg, 409 mmol)
and K
2
CO
3
(3.30 g, 23.9 mmol) at rt after which the solution was
(1H, m, eCHCHe), 4.50 (1H, dd, J 10.4, 6.7 Hz, eCH
J 10.7, 7.9 Hz, eCH e), 4.22e4.13 (2H, m, eCH e), 3.82 (1H, d, J
12.5 Hz, eCH e), 3.62 (1H, d, J 12.5 Hz, eCH e), 3.35 (1H, t, J 6.7 Hz,
eCHe), 2.90 (1H, dd, J 13.7, 6.4 Hz, eCH e), 2.83 (1H, dd, J 13.7,
7.0 Hz, eCH e), 2.56e2.40 (2H, m, eCH
CDCl ): 173.2, 157.3, 137.4, 127.7, 137.3, 133.9, 131.3, 130.9, 128.7,
2
e), 4.40 (1H, dd,
ꢀ
refluxed at 75 C for 18 h. The solvent was removed under reduced
2
2
pressure, H
with EtOAc (2ꢁ50 mL). The organic layers were combined, washed
with brine (50 mL), dried (Na SO ) and the solvent removed under
2
O (50 mL) was added and the aqueous layer extracted
2
2
2
13
2
4
2
2
e). C NMR (125 MHz,
reduced pressure to yield the title compound as a yellow oil (1.40 g,
3
d
ꢂ1
97%). TLC R
f
¼0.25 (Hexane/EtOAc; 19:1). IR
n
max (neat)/cm : 2936
126.2, 121.2, 112.4, 91.8, 62.6, 62.3, 60.9, 47.6, 38.6, 27.9. HRMS
(ESI ) m/z¼464.0740 [MþH]þ found,
þ
C
21
H23NO
127 þ
3
I
required
w (CeH str), 1685 s (C]O str), 1600 s (C]C str), 1485 s (C]C str),
1
1
459 s (C]C str). H NMR (400 MHz, CDCl
.82 (1H, dd, J 7.7, 1.8 Hz, ArH), 7.52 (1H, dt, J 7.2, 1.8 Hz, ArH), 7.01
1H, t, J 7.8 Hz, ArH), 6.96 (1H, d, J 8.4 Hz, ArH), 5.89 (1H, ddt, J 17.1,
0.3, 6.8 Hz, eCHCH ), 5.18 (1H, dq, J 17.1, 1.6 Hz, eCHCH ), 5.12 (1H,
dq, J 10.2,1.7 Hz, eCHCH ), 4.13 (2H, t, J 6.5 Hz, eCH e), 2.60 (2H, tq,
3
):
d
10.49 (1H, s, eCHO),
464.0723.
7
(
1
4.2.21. Synthesis of 2-(but-3-en-1-yloxy)trans-cinnamic acid
(50). To a stirred solution of 48 (1.18 g, 6.76 mmol) in toluene
(120 mL) was added malonic acid (9) (780 mg, 7.45 mmol), pyridine
2
2
2
2
Please cite this article in press as: Ciardiello, J. J.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2015.10.061

J.J. Ciardiello et al. / Tetrahedron xxx (2015) 1e12
11
(
610
m
L, 7.57 mmol) and piperidine (160
m
L, 1.62 mmol). The solu-
2.66e2.56 (3H, m, eCH
1.99e1.92 (1H, m, eCH
2
e & eCHe), 2.51e2.47 (2H, m, eCH
e), 1.86e1.80 (1H, m, eCH
2
e),
ꢀ
tion was refluxed at 120 C with a DeaneStark apparatus for 20 h.
The reaction was quenched with 3M HCl and the solvent removed
2
2
e), 1.75e1.67
e). C NMR (125 MHz,
13
(1H, m, eCH
DMSO-d
2
e), 1.55e1.48 (1H, m, eCH
2
ꢀ
under reduced pressure. H
layer extracted with EtOAc (2ꢁ50 mL). The organic layers were
combined, washed with brine (50 mL), dried (Na SO ) and the
solvent removed under reduced pressure. The crude product was
purified with flash column chromatography, eluting with a gradient
from 20% to 30% EtOAc in hexane and then with 10% MeOH in EtOAc
to yield the title compound as an amorphous orange solid (943 mg,
6
cm : 2917 w br (OeH str), 1677 s (C]O str), 1619 s (C]C str), 1596
s (C]C str), 1491 m (C]C str), 1475 m (C]C str) H NMR (500 MHz,
2
O (50 mL) was added and the aqueous
6
, 120 C):
d
172.9, 166.0, 157.8, 143.1, 136.8, 133.7, 130.7,
129.7, 127.7, 125.5, 121.4, 120.8, 115.5, 114.0, 69.0, 64.0, 46.4, 43.7,
þ
þ
2
4
41.2, 32.3, 31.2, 26.2, 23.0. HRMS (ESI ) m/z¼382.2018 [MþH]
þ
found, C23
H
28NO
4
required 382.2018.
Acknowledgements
ꢀ
4%). Mp 78e80 C. TLC R
f
¼0.25 (Hexane/EtOAc 7:3). IR
nmax (neat)/
The research leading to these results has received funding from
the European Research Council under the European Union’s Sev-
enth Framework Programme (FP7/2007-2013)/ERC grant agree-
ment no [279337/DOS]. In addition, the group research was
supported by grants from the Engineering and Physical Sciences
Research Council, Biotechnology and Biological Sciences Research
Council, Medical Research Council and Wellcome Trust.
ꢂ1
1
CDCl
ArH), 7.35 (1H, ddd, J 8.2, 7.6, 1.8 Hz, ArH), 6.97 (1H, t, J 7.6 Hz, ArH),
.92 (1H, d, J 8.2 Hz, ArH), 6.60 (1H, d, J 16.2 Hz, eCHCHe), 5.93 (1H,
ddt, J 17.1, 10.0, 6.7 Hz, eCHCH e), 5.23 (1H, dq, J 17.4, 1.8 Hz,
eCHCH e), 5.16 (1H, dq, J 10.4, 1.8 Hz, eCHCH e), 4.11 (2H, t, J
.4 Hz, eCH e), 2.63 (2H, tq, J 6.7, 1.5 Hz, eCH
125 MHz, CDCl
3
): d 8.08 (1H, d, J 16.2 Hz, eCHCHe), 7.52 (1H, dd, J 7.6, 1.5 Hz,
6
2
2
2
Data accessibility: all data supporting this study are provided as
Supplementary data accompanying this paper.
13
6
(
1
2
2
e). C NMR
3
):
d
172.2, 157.9, 142.5, 134.1, 131.8, 129.6, 123.2,
þ
20.8, 117.8, 117.6, 112.1, 67.7, 33.7. HRMS (ESI ) m/z¼219.1009
Supplementary data
þ
þ
3
[MþH] found, C13
H
15
O
required 219.1016.
Supplementary data (Copies of 1H NMR and 13C NMR spectra)
associated with this article can be found in the online version, at
http://dx.doi.org/10.1016/j.tet.2015.10.061.
4
(
.2.22. Synthesis of amide (51). 28 (222 mg, 1.02 mmol) and 50
267 mg, 1.22 mmol) were dissolved in EtOAc (10 mL) at rt and then
ꢀ
cooled to 0 C. To this solution was added DIPEA (838
mL,
4
.81 mmol) and a solution of 50% T3P in EtOAc (970
m
L, 1.63 mmol).
ꢀ
References and notes
The solution was stirred at 0 C for 30 min and rt for 18 h. The
reaction was quenched with H
added. The organic layer was separated and washed with 5%
NaHCO
(2ꢁ100 mL), 5% citric acid (100 mL) and then brine (70 mL).
The organic extract was dried (MgSO ) and the solvent removed
under reduced pressure to yield the title compound as a colourless
2
O (100 mL) and EtOAc (100 mL) was
1
. O’Connell, K. M.; Hodgkinson, J. T.; Sore, H. F.; Welch, M.; Salmond, G. P.; Spring,
D. R. Angew. Chem., Int. Ed. 2013, 52, 10706e10733.
2. Russell, A. D. J. Appl. Microbiol. Symp. Supp. 2002, 92, 1Se3S.
3
3
. Galloway, W. R. J. D.; Bender, A.; Welch, M.; Spring, D. R. Chem. Commun. 2009,
446e2462.
. Yu, X. F.; Sun, D. Q. Molecules 2013, 18, 6230e6268.
4
2
4
1
oil (280 mg, 72%). TLC R
f
¼0.72 (PE 30-40/EtOAc 4:6). H NMR
5. Newman, D. J.; Cragg, G. M. Bioactive Macrocycles from Nature In Macrocycles in
Drug Discovery; Levin, J., Ed.; The Royal Society of Chemistry: Cambridge, 2015;
pp 1e36.
ꢀ
(
(
500 MHz, DMSO-d
6
, 120 C):
d
7.68 (1H, d, J 15.5 Hz, eCHCHe), 7.61
1H, d, J 7.9 Hz, ArH), 7.33 (1H, t, J 8.2 Hz, ArH), 7.12 (1H, d, J 15.8 Hz,
6. Macrocycles in Drug Discovery; Levin, J., Ed.; The Royal Society of Chemistry:
eCHCHe), 7.07 (1H, d, J 8.2 Hz, ArH), 6.99 (1H, t, J 7.8 Hz, ArH),
.00e5.89 (1H, m, eCHCH ), 5.20 (1H, d, J 17.3 Hz, eCH e), 5.11 (1H,
d, J 10.1 Hz, eCH ), 4.26e4.10 (5H, m, eCH e), 3.92 (1H, d, J 12.9 Hz,
eCH e), 3.32 (1H, t, J 9.1 Hz, eCH e), 3.27e3.19 (1H, m, eCH e),
.61e2.48 (6H, m, eCH e, eCHe & eCH), 2.06e1.98 (1H, m,
eCH e), 1.82e1.71 (2H, m, eCH
NMR (125 MHz, DMSO-d
Cambridge, 2015.
7
8
. Madsen, C. M.; Clausen, M. H. Eur. J. Org. Chem. 2011, 3107e3115.
. Driggers, E. M.; Hale, S. P.; Lee, J.; Terrett, N. K. Nat. Rev. Drug Discov. 2008, 7,
08e624.
6
2
2
2
2
6
2
2
2
9. O’Connell, K. M.; Beckmann, H. S.; Laraia, L.; Horsley, H. T.; Bender, A.; Ven-
kitaraman, A. R.; Spring, D. R. Org. Biomol. Chem. 2012, 10, 7545e7551.
10. Beckmann, H. S. G.; Nie, F. L.; Hagerman, C. E.; Johansson, H.; Tan, Y. S.; Wilcke,
D.; Spring, D. R. Nat. Chem. 2013, 5, 861e867.
1. Marsault, E.; Peterson, M. L. J. Med. Chem. 2011, 54, 1961e2004.
12. Jefferson, E. A.; Swayze, E. E.; Osgood, S. A.; Miyaji, A.; Risen, L. M.; Blyn, L. B.
2
2
1
3
2
2
e), 1.55e1.45 (1H, m, eCH
2
e).
172.7, 165.9, 157.6, 136.7, 135.1,
30.9, 129.2, 125.1, 121.3, 120.1, 117.2, 113.8, 81.0, 72.0, 68.5, 62.4,
C
ꢀ
, 120 C): d
6
1
1
4
þ
Bioorg. Med. Chem. Lett. 2003, 13, 1635e1638.
5.8, 44.4, 41.6, 33.5, 27.2, 24.4, 19.0. HRMS (ESI ) m/z¼404.1848
1
3. Wessjohann, L. A.; Ruijter, E.; Garcia-Rivera, D.; Brandt, W. Mol. Divers. 2005, 9,
71e186.
4. Isidro-Llobet, A.; Hadje Georgiou, K.; Galloway, W. R. J. D.; Giacomini, E.;
þ
þ
[MþNa] found, C23
4
H27NO Na required 404.1838.
1
1
Hansen, M. R.; Mendez-Abt, G.; Tan, Y. S.; Carro, L.; Sore, H. F.; Spring, D. R. Org.
Biomol. Chem. 2015, 13, 4570e4580.
5. Galloway, W. R. J. D.; Isidro-Llobet, A.; Spring, D. R. Nat. Commun., 1e13, http://
dx.doi.org/10.1038/ncomms1081.
16. Sauer, W. H. B.; Schwarz, M. K. J. Chem. Inf. Comput. Sci. 2003, 43, 987e1003.
7. Sauer, W. H. B.; Schwarz, M. K. Chimia 2003, 57, 276e283.
8. For some examples of the synthesis and phenotypic screening of macrocylic
4
.2.23. Synthesis of macrocycle (21). To a stirred solution of 51
mol) in CH Cl (313 mL) was added Grubb’s second
generation catalyst (45.0 mg, 53.0
(
205 mg, 537
m
2
2
1
m
mol). The solution was sub-
ꢀ
sequently degassed and refluxed at 55 C for 2 h under an ethylene
atmosphere. To this solution was added Grubb’s second generation
1
1
catalyst (90.0 mg, 106
m
mol), after which the solution was degassed
collections, see: (a) Jimmidi, R.; Shroff, G. K.; Satyanarayana, M.; Reddy, B. R.;
Kapireddy, J.; Sawant, M. A.; Sitaswad, S. L.; Arya, P.; Mitra, P. Eur. J. Org. Chem.
ꢀ
and refluxed at 55 C for 28 h under an argon atmosphere. The
solvent was removed under reduced pressure and the crude
product purified with flash column chromatography, eluting with
2014, 1151e1156; (b) Aeluri, M.; Pramanik, C.; Chetia, L.; Mallurwar, N. K.; Ba-
lasubramanian, S.; Chandrasekar, G.; Kitambi, S. S.; Arya, P. Org. Lett. 2013, 15,
436e439; (c) Guduru, S. K. R.; Chamakuri, S.; Chandrasekar, G.; Kitambi, S. S.;
Arya, P. ACS Med. Chem. Lett. 2013, 4, 666e670; (d) Aeluri, M.; Dasari, B.; Arya, P.
Org. Lett. 2015, 17, 472e475.
9. Marsault, E. Macrocycles as Templates for Diversity Generation, in Drug Dis-
covery In Diversity Oriented Synthesis: Basics and Applications in Organic Syn-
thesis, Drug Discovery, and Chemical Biology; Trabocchi, A., Ed.; John Wiley &
Sons: Hoboken, New Jersey, 2013; pp 253e287.
0. Nielsen, T. E.; Schreiber, S. L. Angew. Chem., Int. Ed. 2008, 47, 48e56.
1. Schreiber, S. L. Science 2000, 287, 1964e1969.
22. Ta, D. S. Nat. Chem. Biol. 2005, 1, 74e84.
3. Hill, N.; Du, L.; Wang, Q. DOS-Derived Small-Molecule Probes in Chemical Bi-
ology In Diversity Oriented Synthesis: Basics and Applications in Organic Syn-
thesis, Drug Discovery, and Chemical Biology; Trabocchi, A., Ed.; John Wiley &
Sons: Hoboken, New Jersey, 2013; pp 575e618.
3
0% EtOAc in hexane to yield the title compound as a brown crys-
talline solid (64.9 mg, 32%). TLC R
f
¼0.26 (Hexane/EtOAc 4:6). IR
1
ꢂ1
n
max (neat)/cm : 2933 w (CeH str), 1722 s (C]O str), 1641 s (C]O
1
str), 1598 s (C]O str), 1489 m (C]C str). H NMR (500 MHz, DMSO-
ꢀ
d
6
, 120 C):
d
¼7.64 (1H, d, J 15.8 Hz, eCHCHe), 7.53 (1H, d, J 7.8 Hz,
2
2
ArH), 7.32 (1H, t, J 7.3 Hz, ArH), 7.11e7.06 (2H, m, ArH), 6.98 (1H, t, J
.3 Hz, ArH), 6.19 (1H, d, J 15.8 Hz, eCHCH-), 6.02 (1H, dt, J 15.8,
.9 Hz, eCHCHe), 5.01 (1H, s, eCH ), 4.93 (1H, s, eCH ) 4.28e4.16
4H, m, eCH e), 4.12e4.07 (1H, m, eCH e), 3.80e3.74 (1H, m,
e), 3.50e3.42 (1H, m, eCH e), 3.41e3.34 (1H, m, eCH e),
7
6
(
2
2
2
2
2
eCH
2
2
2
Please cite this article in press as: Ciardiello, J. J.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2015.10.061

12
J.J. Ciardiello et al. / Tetrahedron xxx (2015) 1e12
2
2
2
4. Wyatt, E. E.; Fergus, S.; Galloway, W. R. J. D.; Bender, A.; Fox, D. J.; Plowright, A. 34. Maurya, S. K.; Dow, M.; Warriner, S.; Nelson, A. Beilstein J. Org. Chem. 2013, 9,
T.; Jessiman, A. S.; Welch, M.; Spring, D. R. Chem. Commun. 2006, 3296e3298.
5. Wyatt, E. E.; Galloway, W. R. J. D.; Thomas, G. L.; Welch, M.; Loiseleur, O.;
Plowright, A. T.; Spring, D. R. Chem. Commun. 2008, 4962e4964.
6. Thomas, G. L.; Spandl, R. J.; Glansdorp, F. G.; Welch, M.; Bender, A.; Cockfield, J.;
Lindsay, J. A.; Bryant, C.; Brown, D. F. J.; Loiseleur, O.; Rudyk, H.; Ladlow, M.;
Spring, D. R. Angew. Chem., Int. Ed. 2008, 47, 2808e2812.
775e785.
35. Mullard, A. Nat. Rev. Drug Discov. 2012, 11, 172e174.
36. Horne, W. S.; Olsen, C. A.; Beierle, J. M.; Montero, A.; Ghadiri, M. R. Angew.
Chem., Int. Ed. 2009, 48, 4718e4724.
37. Bock, V. D.; Speijer, D.; Hiemstra, H.; van Maarseveen, J. H. Org. Biomol. Chem.
2007, 5, 971e975.
2
2
2
7. Socha, A. M.; Tan, N. Y.; LaPlante, K. L.; Sello, J. K. Bioorg. Med. Chem. 2010, 18,
38. Trabocchi, A. Diversity-oriented Synthesis of Amino-acid Derived Scaffolds and
Peptidomimetics: A Perspective In Diversity Oriented Synthesis: Basics and Ap-
plications in Organic Synthesis, Drug Discovery, and Chemical Biology; Trabocchi,
A., Ed.; John Wiley & Sons: Hoboken, New Jersey, 2013; pp 177e200.
39. Preliminary studies indicated that alkylation of the hydroxyl group in the
presence of a free acid group was somewhat capricious. Therefore, when car-
rying out the full synthesis, it was decided to mask the acid group as an ester
prior to alkylation. In addition, preliminary studies had demonstrated that
azido-tosylate 38 was prone to elimination rather than substitution when re-
acted with compound 40. It was ascertained that replacing the tosylate group
with a bromide (compound 24) greatly encouraged the desired substitution
reaction and minimised the risk of elimination occurring.
7193e7202.
8. Kantevari, S.; Patpi, S. R.; Addla, D.; Putapatri, S. R.; Sridhar, B.; Yogeeswari, P.;
Sriram, D. ACS Comb. Sci. 2011, 13, 427e435.
9. Isidro-Llobet, A.; Murillo, T.; Bello, P.; Cilibrizzi, A.; Hodgkinson, J. T.; Galloway,
W. R. J. D.; Bender, A.; Welch, M.; Spring, D. R. Proc. Natl. Acad. Sci. U.S.A. 2011,
108, 6793e6798.
30. Grossmann, A.; Bartlett, S.; Janecek, M.; Hodgkinson, J. T.; Spring, D. R. Angew.
Chem., Int. Ed. 2014, 53, 13093e13097.
31. Wessjohann, L. A.; Voigt, B.; Rivera, D. G. Angew. Chem., Int. Ed. 2005, 44,
785e4790.
4
3
2. Marcaurelle, L. A.; Comer, E.; Dandapani, S.; Duvall, J. R.; Gerard, B.; Kesavan, S.;
Lee, M. D. t.; Liu, H.; Lowe, J. T.; Marie, J. C.; Mulrooney, C. A.; Pandya, B. A.;
Rowley, A.; Ryba, T. D.; Suh, B. C.; Wei, J.; Young, D. W.; Akella, L. B.; Ross, N. T.;
Zhang, Y. L.; Fass, D. M.; Reis, S. A.; Zhao, W. N.; Haggarty, S. J.; Palmer, M.; Foley,
M. A. J. Am. Chem. Soc. 2010, 132, 16962e16976.
40. There was no evidence for the formation of the analogous 1,5-disubstituted
triazole-containing species in this reaction.
41. Muller, P. U.; Weber, E.; Rheinwald, G.; Seichter, W. Org. Biomol. Chem. 2005, 3,
3757e3766.
33. Kopp, F.; Stratton, C. F.; Akella, L. B.; Tan, D. S. Nat. Chem. Biol. 2012, 8, 358e365.
Please cite this article in press as: Ciardiello, J. J.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2015.10.061